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Abstract:

There is provided a choke coil, including: a core part having first and
second legs; a winding part having a first coil wound around the first
leg and a second coil wound around the second leg; and a sectioning wall
partitioning the winding part into several winding regions.

Claims:

1. A choke coil, comprising: a core part having first and second legs; a
winding part having a first coil wound around the first leg and a second
coil wound around the second leg; and a sectioning wall partitioning the
winding part into several winding regions.

2. The choke coil of claim 1, wherein the winding part has at least one
of the first coil and the second coil wound in a first axial direction
perpendicular to the first leg and the second leg.

3. The choke coil of claim 1, wherein the winding part has at least one
of the first coil and the second coil wound in a second axial direction
parallel to the first leg and the second leg.

4. The choke coil of claim 2, wherein a first turns amount that at least
one of the first coil and the second coil is wound at in the first axial
direction in the first winding region is different from a second turns
amount that at least one of the first coil and the second coil is wound
at in the first axial direction in the second winding region.

5. The choke coil of claim 3, wherein a first turns amount that at least
one of the first coil and the second coil is wound at in the second axial
direction in the first winding region is different from a second turns
amount that at least one of the first coil and the second coil is wound
at in the second axial direction in the second winding region.

6. The choke coil of claim 1, wherein the sectioning wall includes: a
first sectioning wall partitioning a region in which the first coil is
wound into several regions; and a second sectioning wall partitioning a
region in which the second coil is wound into several regions.

7. The choke coil of claim 6, wherein the first coil wound in the first
winding region and the first coil wound in the second winding region are
contiguous through the first sectioning wall, and the second coil wound
in the first winding region and the second coil wound in the second
winding region are contiguous through the second sectioning wall.

8. The choke coil of claim 1, wherein a length of the first winding
region in the second axial direction is different from a length of the
second winding region in the second axial direction.

9. A power supply device, comprising: a power input unit supplying input
power; an EMI filter unit removing noise from the input power; and a
converter unit converting power supplied from the EMI filter unit,
wherein the EMI filter unit includes: a core part having first and second
legs; a winding part having a first coil wound around the first leg and a
second coil wound around the second leg; and a sectioning wall
partitioning the winding part into several winding regions.

10. The power supply device of claim 9, wherein the winding part has at
least one of the first coil and the second coil wound in a first axial
direction perpendicular to the first leg and the second leg.

11. The power supply device of claim 9, wherein the winding part has at
least one of the first coil and the second coil wound in a second axial
direction parallel to the first leg and the second leg.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of Korean Patent Application
No. 10-2013-0104098 filed on Aug. 30, 2013, with the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.

BACKGROUND

[0002] The present disclosure relates to a choke coil with reduced
parasitic capacitance and a power supply device including the same.

[0003] Recently, in the field of flat panel displays (FPDs) such as liquid
crystal displays (LCDs), plasma display panels (PDPs), organic light
emitting diodes (OLEDs), such products have become smaller and slimmer,
and processing speeds thereof have increased. Under these circumstances,
noise from electromagnetic waves may cause various problems in such
devices.

[0005] A SMPS is a modular power supply device that converts externally
supplied electricity into electricity usable in various types of
electric/electronic devices such as a computer, a TV, a wireless
communication device and the like. It serves to convert household power
into high efficiency/high quality power as required by various electronic
devices by way of using the switching of semiconductor devices and a
power conversion function of a transformer.

[0006] In operation, however, a SMPS is accompanied by various noise
caused by electromagnetic interference (EMI) generated when switching
operation is made.

[0007] In particular, a flat panel display may have a relatively large
amount of electromagnetic noise generated therein by a power converter,
an image board, a semiconductor device and the like, which operate in a
switching manner, and thus various types of EMI filter are used therein
to suppress electromagnetic wave noise.

[0008] Electromagnetic wave noise may be largely classified into conducted
emissions (CE) and radiated emissions (RE), each of which may be further
classified into differential-mode noise and common-mode noise. An EMI
filter to reduce differential-mode noise commonly uses a normal-mode
choke and an X-capacitor, while an EMI filter to reduce common-mode noise
commonly uses a common-mode choke and a Y-capacitor.

[0009] In particular, as the operating speeds of SMPSs are increased, EMI
noise in a high frequency band (approximately 1 MHz or higher) may occur
excessively, and a common-mode choke coil for high frequencies is
typically used for attenuating noise in the high-frequency band.

[0010] A typical toroidal type common-mode choke has high parasitic
capacitance so that resonant frequency distribution is low. Accordingly,
separate common-mode chokes are required in a high-frequency band and a
low-frequency band. This is disadvantageous in terms of configuring a
simple EMI circuit. Moreover, this requires manual intervention so that
productivity is lowered and product quality may not be maintained.

[0013] An aspect of the present disclosure may provide a choke coil with
reduced parasitic capacitance.

[0014] An aspect of the present disclosure may also provide a choke coil
that may be automatically wound and thus may increase production yield
and save manufacturing costs.

[0015] An aspect of the present disclosure may also provide an EMI filter
that has a high resonant frequency so as to be applied in both high- and
low-frequency bands.

[0016] According to an aspect of the present disclosure, a choke coil may
include: a core part having first and second legs; a winding part having
a first coil wound around the first leg and a second coil wound around
the second leg; and a sectioning wall partitioning the winding part into
several winding regions.

[0017] The winding part may have at least one of the first coil and the
second coil wound in a first axial direction perpendicular to the first
leg and the second leg.

[0018] The winding part may have at least one of the first coil and the
second coil wound in a second axial direction parallel to the first leg
and the second leg.

[0019] A first turns amount that at least one of the first coil and the
second coil is wound at in the first axial direction in the first winding
region may be different from a second turns amount that at least one of
the first coil and the second coil is wound at in the first axial
direction in the second winding region.

[0020] A first turns amount that at least one of the first coil and the
second coil is wound at in the second axial direction in the first
winding region may be different from a second turns amount that at least
one of the first coil and the second coil is wound at in the second axial
direction in the second winding region.

[0021] The sectioning wall may include: a first sectioning wall
partitioning a region in which the first coil is wound into several
regions, and a second sectioning wall partitioning a region in which the
second coil is wound into several regions.

[0022] The first coil wound in the first winding region and the first coil
wound in the second winding region may be contiguous through the first
sectioning wall, and the second coil wound in the first winding region
and the second coil wound in the second winding region may be contiguous
through the second sectioning wall.

[0023] A length of the first winding region in the second axial direction
may be different from a length of the second winding region in the second
axial direction.

[0024] According to another aspect of the present disclosure, a power
supply device may include: a power input unit supplying input power; an
EMI filter unit removing noise from the input power; and a converter unit
converting power supplied from the EMI filter unit, wherein the EMI
filter unit includes: a core part having first and second legs; a winding
part having a first coil wound around the first leg and a second coil
wound around the second leg; and a sectioning wall partitioning the
winding part into several winding regions.

BRIEF DESCRIPTION OF DRAWINGS

[0025] The above and other aspects, features and other advantages of the
present disclosure will be more clearly understood from the following
detailed description taken in conjunction with the accompanying drawings,
in which:

[0032] FIGS. 7A and 7B are views showing coils wound according to other
exemplary embodiments of the present disclosure;

[0033] FIGS. 8A and 8B are views showing coils wound according to other
exemplary embodiments of the present disclosure;

[0034] FIG. 9 is a graph showing impedance characteristics of a choke coil
with an unpartitioned region and impedance characteristics of a choke
coil with partitioned winding regions;

[0035] FIG. 10 is a circuit diagram in which the choke coil according to
an exemplary embodiment of the present disclosure is employed as an EMI
filter;

[0036] FIG. 11 is a graph showing results of measuring EMI from an EMI
filter according to the related art; and

[0037] FIG. 12 is a graph showing results of measuring EMI from an EMI
filter employing the choke coil according to an exemplary embodiment of
the present disclosure.

DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present invention will be described
in detail with reference to the accompanying drawings. The invention may,
however, be embodied in many different forms and should not be construed
as being limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough and
complete, and will fully convey the scope of the invention to those
skilled in the art. In the drawings, the shapes and dimensions of
elements may be exaggerated for clarity, and the same reference numerals
will be used throughout to designate the same or like elements.

[0039] FIG. 1 is a block diagram of a flat panel display.

[0040] Referring to FIG. 1, the flat panel display may include a power
quality management unit, a power conversion unit, and a load.

[0041] The load may include a light-emitting diode.

[0042] The power conversion unit may include a rectification stage, a
phase compensation unit, and a switched-mode DC/DC converter. The
switched-mode DC/DC converter may include a flyback converter, for
example, and may employ various isolated converter topologies.

[0043] A significant amount of electromagnetic interference (EMI) may
occur, since abrupt changes in current and voltage occur in a DC/DC
converter, and image modes and semiconductor devices are manufactured to
be smaller and faster.

[0044] In order to suppress EMI, an EMI filter may be disposed before a
rectifier.

[0045] FIG. 2 shows a typical EMI filter.

[0046] Referring to FIG. 2, the EMI filter may include a CM choke for low
frequencies 10 and a CM choke for high frequencies so as to attenuate
noise in low-frequency band and high-frequency band, respectively.

[0047] The EMI filter requires two magnetic elements, so that the unit
price and volume are increased.

[0048] FIGS. 3A through 3C show a typical common-mode choke coil.

[0049] Referring to FIG. 3A, the common-mode choke coil may include a core
part 32 and a winding part 35.

[0050] FIG. 3B is a cross-sectional view of the common-mode choke coil
shown in FIG. 3A.

[0051] The core part 32 may include a first leg 33 and a second leg 34.
Around the first leg 33 and the second leg 34, coils are wound.

[0052] The winding part 35 may include a first coil 35-1 and a second coil
35-2.

[0053] FIG. 3C shows a winding order in which the first coil 35-1 is wound
around the first leg 33 of the common-mode choke coil.

[0057] FIG. 4B is a view in which the parasitic capacitance in portion A
of FIG. 3C is modeled.

[0058] Here, the values of parasitic capacitance may be represented by
modeling it for each of regions.

[0059] FIG. 4C shows coupled parasitic capacitance modeled in each of the
regions.

[0060] As shown in FIG. 4C, the parasitic capacitances C1, C2 and C3 in
the respective regions are connected in parallel, and the parasitic
capacitance in each of the regions may be calculated as follows:

Ctotal=C1+C2+C3 [Mathematical Expression 1]

[0061] As can be seen from Mathematical Expression 1, as the turns amount
of the wound coils increases, the parasitic capacitance generated in
parallel increases, and thus the total parasitic capacitance also
increases.

[0062] FIG. 5 is a diagram showing a common-mode choke coil according to
an exemplary embodiment of the present disclosure.

[0063] Referring to FIG. 5A, the common-mode choke coil may include a core
part 110, winding parts 120 and 130, and sectioning walls 140 and 150.

[0064] FIG. 5B is a cross-sectional view of the common-mode choke coil
shown in FIG. 5A.

[0065] The core part 110 may include a first leg 112 and a second leg 114.
Around the first leg 112 and the second leg 114, coils are wound. Here,
the leg around which a first coil 120 is wound is defined as a first leg
112, and the leg around which a second coil 130 is wound is defined as a
second leg 114.

[0066] The winding part 120 may include the first coil 120 and the second
coil 130.

[0067] As shown in FIG. 5, the first coil 120 may be wound in a first
axial direction. Here, the first axial direction refers to a direction
perpendicular to the first and second legs 112 and 114.

[0068] Further, the second coil 130 may be wound in the first axial
direction.

[0069] As shown in FIG. 5, the first coil 120 may be wound in a second
axial direction. Here, the second axial direction refers to a direction
parallel to the first and second legs 112 and 114.

[0070] Further, the second coil 130 may be wound in the second axial
direction.

[0071] The sectioning walls may section the winding part into several
winding regions.

[0072] Specifically, a first sectioning wall 140 may section the region in
which the first coil 120 is wound into several winding regions.

[0073] Referring to FIG. 5B, the first sectioning wall 140 may section the
region in which the first coil 120 is wound into three winding regions I,
II, and III.

[0074] For example, by two first sectioning walls 140-1 and 140-2, the
region in which the first coil 120 is wound may be partitioned into three
winding regions (a first winding region I, a second winding region II,
and a third winding region III).

[0075] Although the region is partitioned into the winding regions I, II,
and III, the first coil 120 may be contiguous through the first
sectioning walls 140-1 and 140-2.

[0076] Specifically, a second sectioning wall 150 may section the region
in which the second coil 130 is wound into several winding regions.

[0077] Referring to FIG. 5B, the second sectioning wall 150 may section
the region in which the second coil 130 is wound into three winding
regions I, II, and III.

[0078] For example, by virtue of two second sectioning walls 150-1 and
150-2, the region in which the second coil 130 is wound may be
partitioned into three winding regions (a first winding region I, a
second winding region II, and a third winding region III).

[0079] Although the region is partitioned into the winding regions I, II,
and III, the second coil 130 may be contiguous through the second
sectioning walls 150-1 and 150-2.

[0080] FIG. 5C shows a winding order in which the first coil 120 is wound
around the first leg 112 of the common-mode choke coil.

[0084] It is to be noted that only the end portion of the coil wound in
the first winding region I and the end portion of the coil wound in the
second winding region II are connected to each other but the other
portions of the coil wound in the first winding region I and of the coil
wound in the second winding region II are separated by the first
sectioning wall.

[0085] FIG. 6B is a view in which the parasitic capacitance in portion B
of FIG. 5C is modeled.

[0086] Here, the values of parasitic capacitance may be represented by
being modeled for each of the regions.

[0087] As shown in FIG. 6B, the parasitic capacitance in the first winding
region I and the parasitic capacitance in the second winding region II
are connected in series. Further, the parasitic capacitance in the second
winding region II and the parasitic capacitance in the third winding
region III are connected in series.

[0088] FIG. 6C shows coupled parasitic capacitance modeled in each of the
regions.

[0089] As shown in FIG. 6C, the parasitic capacitances C1, C2 and C3 in
the respective regions are connected in series, and the parasitic
capacitance in the regions may be calculated as follows:

1/Ctotal=1/C1+1/C2+1/C3 [Mathematical Expression 2]

[0090] As can be seen from Mathematical Expression 2, as the number of
winding regions separated by the sectioning walls increases, the
parasitic capacitance generated in series increases, and thus the total
amount of parasitic capacitance may be decreased.

[0091] That is, the choke coil according to an exemplary embodiment of the
present disclosure may reduce stray capacitance between coils.
Accordingly, the first resonant frequency may move to a high-frequency
band in an impedance graph of the common-mode choke. Therefore, the
common-mode choke according to an exemplary embodiment of the present
disclosure may widen the bandwidth of impedance so that EMI noise after
the first resonant band may be effectively removed.

[0092] FIG. 7 shows a method of winding a coil according to another
exemplary embodiment of the present disclosure.

[0093] As can be seen from Mathematical Expression 2, the value of the
total capacitance Ctotal is smaller than the smallest parasitic
capacitance among the parasitic capacitances generating in the winding
regions.

[0094] Here, the total parasitic capacitance may be less than the
parasitic capacitance of a winding region even if the levels of parasitic
capacitance in other winding regions are very high, by way of designing
the parasitic capacitance of the winding region to be low.

[0098] Referring to FIG. 7B, a first turns amount that a coil is wound in
the first axial direction in the first winding region may be different
from a second turns amount that the coil is wound in the first axial
direction in the second winding region. For instance, the second turns
amount may be larger than the first turns amount.

[0099] In FIG. 7B, the parasitic capacitance may be calculated as follows:

[0100] Because the total parasitic capacitance is smaller than the
parasitic capacitance in the first winding region or the third winding
region in which the coil is unevenly wound, the method of winding shown
in FIG. 7B may further reduce the parasitic capacitance compared to the
method of winding shown in FIG. 7A.

[0101] FIG. 8 shows a method of winding a coil according to another
exemplary embodiment of the present disclosure.

[0105] Referring to FIG. 8B, a first turns amount that a coil is wound in
the second axial direction in the first winding region may be different
from a second turns amount that the coil is wound in the second axial
direction in the second winding region. For instance, the second turns
amount may be larger than the first turns amount.

[0106] In FIG. 8B, the parasitic capacitance may be calculated as follows:

[0107] Because the total parasitic capacitance is lower than the parasitic
capacitance in the first winding region or the third winding region in
which the coil is unevenly wound, the method of winding shown in FIG. 8B
may further reduce the parasitic capacitance compared to the method of
winding shown in FIG. 8A.

[0108] Here, the length of the first winding region in the second axial
direction may be different from the length of the second winding region
in the second axial direction. Further, the length of the second winding
region in the second axial direction may be longer than the length of the
first winding region in the second axial direction.

[0109] FIG. 9 is a graph showing the impedance characteristic of a choke
coil with unpartitioned region and the impedance characteristic of a
choke coil with partitioned winding regions.

[0110] As can be seen from FIG. 9, and the impedance characteristics of
the choke coil with partitioned winding regions according to an exemplary
embodiment of the present disclosure are improved.

[0112] The parasitic capacitances generated according to winding region
section are a major factor in determining the first resonant frequency of
a common-mode choke based on the mathematical expression below:

f = 1 2 π LC [ Mathematical Expression
7 ] ##EQU00001##

[0113] The impedance in a high-frequency band relies heavily on the
location of the first resonant frequency and high frequency
characteristics may be improved based thereon. In addition, the
characteristic also affects on the CE region (150 kHz˜30 MHz) and
the RE region (30 MHz˜200 MHz), so that it advantageously improves
EMI and simplifies an EMI circuit.

[0114] Therefore, in order to meet the impedance requirement necessary for
attenuating noise in a high frequency band, parasitic capacitance may be
adjusted using an appropriate winding manner, such that a common-mode
choke coil may be provided that is automatically wound and has a
plurality of winding regions.

[0115] FIG. 10 is a circuit diagram in which the choke coil according to
an exemplary embodiment of the present disclosure is employed as an EMI
filter.

[0116] The choke coil according to the exemplary embodiment reduces
parasitic capacitance to thereby improve frequency characteristics.
Therefore, when the choke coil according to the exemplary embodiment is
employed as an EMI filter, the EMI filter may be configured with a single
choke coil, unlike a typical two-stage EMI filter.

[0117] FIG. 11 is a graph showing results of measuring EMI from an EMI
filter according to the related art.

[0118] FIG. 12 is a graph showing results of measuring EMI from an EMI
filter employing the choke coil according to an exemplary embodiment.

[0119] Comparing the EMI characteristics of FIGS. 11 and 12, it can be
seen that, in the frequency band from 0.7 MHz to 5 MHz and around 10 MHz,
the single-stage filter employing the common-mode choke with reduced
parasitic capacitance exhibits batter characteristic than the
single-stage EMI filter employing a typical common-mode choke by
approximate 10 dB.

[0120] By employing the choke coil according to an exemplary embodiment of
the present disclosure, a typical two-stage EMI filter may be configured
as a single-stage EMI filter. Accordingly, the number of elements at an
EMI filter stage may be reduced, and thus costs incurred in manufacturing
the EMI filter may be saved.

[0121] Further, since the common-mode choke with reduced parasitic
capacitance and an EMI filter structure use automatic winding, for a
period required for design may be shortened and development costs may be
saved. That is, existing automatic equipment may be used without
adaptation, and thus no further equipment or costs are required, to
thereby save the number of elements and manufacturing cost.

[0122] By doing so, the size of an EMI filter may be reduced.

[0123] As set forth above, according to exemplary embodiments of the
present disclosure, a choke coil with reduced parasitic capacitance may
be provided.

[0124] Further, a choke coil that is automatically wound and thus increase
production yield and saves manufacturing cost may be provided.

[0125] Moreover, an EMI filter that has high resonant frequency so as to
be applied in both high- and low-frequency bands may be provided.

[0126] While exemplary embodiments have been shown and described above, it
will be apparent to those skilled in the art that modifications and
variations could be made without departing from the spirit and scope of
the present disclosure as defined by the appended claims.